Calculation of the muon contamination in a π- meson beam

We present here a method for calculating the μ contamination of a π-meson beam which is parallel and of cylindrical symmetry, and also the so-called 'CONTAMU' programme which makes it possible to carry out this calculation. An evaluation of the μ contamination is necessary for correcting the experimental values (gross) of the cross-sections of the various reactions using the π-meson beam as a beam of incident particles. The following two cases are dealt with: 1 - The beam is defined by an S1 counter: the μ contamination is calculated when the beam passes through this counter. 2 - The beam is defined by 2 counters, S1 and S2: the μ contamination is calculated when the beam passes through the 2 counters successively. After presenting the problem in the first introductory paragraph, we deal in detail in paragraph II with the calculation, following the order of the programme. At the end of paragraph II will be found definitions of a certain number of values which the programme calculates; these are the values of the contamination in one of the two preceding cases integrated in certain well-defined disintegration volumes. In paragraph III is given as an example a table of results for a few values of the parameters. The listing of the 'CONTAMU' programme is given in the appendix. This programme was established in 1963 for correcting the experimental values of the cross-sections obtained during an experiment carried out on the synchrotron Saturne by the Falk-Vairant group. (author)